Averaging Pitot Tube Average Pitot Tube

Product Overview

Averaging Pitot Tube

301 TYPE302 TYPE303 TYPE304 TYPE

Daehan Instruments developed a new pitot tube that resolves several problems of conventional pitot tubes — low differential pressure, the need for precise installation position, and the difficulty of measuring the average velocity in the pipe.

With six months of technical support from the Korea Institute of Industrial Technology starting in 1994, the new pitot tube was successfully developed.

A conventional pitot tube has the advantages of a simple structure and the ability to measure velocity over a relatively small area regardless of pipe size, but it also has the disadvantages of low differential pressure, demanding precision in installation position and orientation, and difficulty in measuring the average velocity in the pipe.

The Daehan pitot tube detects a differential pressure about 2 ~ 3 times greater than a conventional pitot tube, and obtains the average velocity by sensing pressure at 4 ~ 8 points inside the pipe. It saves 5 ~ 8% energy compared with an orifice meter, and its simple construction reduces installation and maintenance costs.

3B ~ 16B / 10B ~ 120BAccuracy ±1.5%STS316 · Inconel · Monel · HastelloyScrew & Flange

English description

DAEHAN INSTRUMENT company worked hard to make a new PITOT TUBE that is solved a many problems in the existing PITOT TUBE such as low pressure drop, require for accuracy of installed location, difficulty of average velocity measurement in pipe. We has technical help from the korea institute of industrial technology for the six months since 1994. and we succeeded in the development of a new PITOT TUBE. Feature of DAEHAN INSTRUMENT CO., LTD. Pitot tube: 1) Easily measurement of the flux — The value of pressure drop is detected about 2~3 times larger than the existing one. 2) Superior efficiency — The pressure drop are observed at 4~8 point in the inner pipe. 3) Retrenchment of energy — This products are 5~8% better as compared with the orifice meter. 4) Reduction of construction expenses and upkeep costs because of a simple equipment.

Measurement principle

Differential-pressure structure and flow relationship

The velocity of an incompressible fluid is obtained from the Bernoulli equation. Q = A·V = A·√(2g(P₁ − P₂)/r) … Eq. (1). P₁: total pressure, P₂: static pressure, V: velocity, A: pipe cross-sectional area, r: specific gravity.

In practice, the velocity/pressure coefficient C obtained from experimental data is applied, and the flow is calculated as Q = A·V = A·C·√(2g(P₁ − P₂)/r) … Eq. (2).

Taking the velocity profile in the pipe (Figure 2) into account, the sensing holes are placed at the equal-area division positions rᵢ/R. n = 2: 0.5, 0.866 / n = 3: 0.408, 0.707, 0.912 / n = 4: 0.354, 0.612, 0.790, 0.936.

Types · model configuration

Specification comparison by model

Photographic images by type. Connection sizes, materials and other details follow the ordering code.

Item	301 TYPE Single support type (Single support)	302 TYPE Double support type (Double support)	303 TYPE Isolation valve type	304 TYPE Isolation valve & Rod type
Features	Easy to install	Suitable for large caliber (suitable for large pipe sizes)	Shut-off fluid after remove element on maintenance (fluid is shut off after removing the element for maintenance)	Installation & maintenance can be done in operation (installation and maintenance possible during operation)
Type	Single support type — suitable for low pressure (10K or less) and ducts, simple construction, applicable sizes 3B ~ 16B	Double support type — suitable for high pressure (10 ~ 20K) and large pipe sizes (10 ~ 120B), handles high velocities	Isolation Valve type — fitted with an isolation valve to prevent liquid overflow from the tube during maintenance and repair	Isolation valve & Rod type — overflow prevention system for maintenance and repair under high-pressure conditions (insertion rod · packing gland · cage nipple)
Applicable piping	3B ~ 16B Pipe & Duct	10B ~ 120B Pipe & Duct	3B ~ 16B Pipe & Duct	3B ~ 16B Pipe & Duct
Materials	STS316, Inconel, Monel, Hastelloy	STS316, Inconel, Monel, Hastelloy	STS316, Inconel, Monel, Hastelloy	STS316, Inconel, Monel, Hastelloy
Connection	Screw & Flange	Screw & Flange	Screw & Flange	Screw & Flange
Measured fluid	Liquid & Gas not included sludge (not for high-viscosity fluids)	Liquid & Gas not included sludge (not for high-viscosity fluids)	Liquid & Gas not included sludge (not for high-viscosity fluids)	Liquid & Gas not included sludge (not for high-viscosity fluids)
Accuracy	±1.5%	±1.5%	±1.5%	±1.5%

Technical Specifications

Detailed conditions are confirmed at quotation.

Item	Value
Accuracy	±1.5%
Measured fluid	Liquids and gases not containing sludge (not for high-viscosity fluids)
Applicable pipe sizes	301 / 303 / 304 TYPE: 3B ~ 16B · 302 TYPE: 10B ~ 120B (Pipe & Duct)
Pressure classes	Single support type (301): low pressure (10K or less) and ducts · double support type (302): high pressure (10 ~ 20K), high velocity
Sensor material	STS316, Inconel, Monel, Hastelloy
Mounting connection	Screw & Flange ※ Ordering codes: PT1", PT1-1/2, PT2" · JIS 10K / 20K 40A · 50A · 80A · ANSI 150# / 300# 1-1/2B · 2B · 3B
DP (D/P) connection	PT 1/2 · PT 3/8 · PT 1/4
Differential-pressure characteristics	About 2 ~ 3 times the differential pressure of a conventional pitot tube · pressure sensed at 4 ~ 8 points inside the pipe
Energy	5 ~ 8% better than an orifice meter
Isolation valve material (Body / Ball)	SCPH2/316 · SCPH13/316 · 304/316 · 316/316 · Option (303, 304 TYPE)
Packing · cage nipple · insertion rod material	Packing: Rubber, Teflon, Graphite / Cage Nipple: Carbon steel, Stainless steel / Insertion Rods: Carbon steel, Stainless steel (304 TYPE)
Installation angle tolerance	Tilt within the pipe cross-section ±3° · tilt along the pipe axis ±5° · sensing hole orientation ±3°

Dimensions · drawings

Unit: mm. Actual manufacturing dimensions are based on the approved drawing.

Required straight run (Table 4, multiples of D)

Upstream piping condition	Without conditioner		With conditioner			Downstream
Piping condition	A (same plane)	A (different planes)	A′	A	C′	B
Single 90° elbow	7	9	6	3	3	3
Two 90° elbows (same plane)	9	14	8	4	4	3
Two 90° elbows (different planes)	19	24	9	4	5	4
Reducer	8	8	8	4	4	3
Expander	8	8	8	4	4	3
Valve	24	24	9	4	5	4

A: upstream straight run, B: downstream straight run, A′ / C′: with a flow conditioner, upstream of the conditioner / conditioner to pitot tube. Figures: A = upstream straight run, B = downstream straight run, A′ = elbow to flow conditioner, C′ = conditioner to pitot tube (unit: multiples of pipe inner diameter D).

Equal-area division positions rᵢ/R (Figure 2 velocity profile)

n: number of radial divisions, rᵢ/R: ratio of the sensing point position to the pipe radius.

Installation orientation in horizontal piping (Figures 6, 7)

The diagrams in Pitot Tube catalog p.5 Figure 6 (Liquids) and Figure 7 (Gases), arranged as a table.

Installation requirements

Straight run and installation notes

• In vertical piping, the pitot tube is installed at a position in the horizontal plane (Figure 5).
• In horizontal piping, the installation method is chosen according to the type of fluid. For liquids it is installed at the bottom of the pipe (Figure 6), for gases at the top (Figure 7).
• The required straight run follows Table 4 according to the upstream piping condition and whether a flow conditioner is installed.
• The installation angle tolerances are ±3° within the pipe cross-section, ±5° along the pipe axis and ±3° in sensing hole orientation (Figure 8).
• Precautions: avoid locations with heavy dust (if the sensing holes become blocked by dust, this can be cleared by blowing high-pressure air). Not suitable for turbulent flow. Do not use for high-pressure steam or in locations subject to vibration.

Ordering information (How to Order)

You can request a quotation by combining the model codes.

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